This invention relates generally to communications systems for linking peripheral devices to a computer and particularly to apparatus for linking two separate devices to a keyboard input of a computer.
The recently introduced Sun MCA 3000 Modular Computer Analyzer for diagnostic testing of automotive engines and the like is centered about an IBM compatible PC. The MCA 3000 Analyzer incorporates a keyboard by which a user-technician may input commands to the diagnostic analyzer. A remote control device is also provided to enable control of the analyzer by the input of commands from a remote location, for example at the site of the engine under test. The present invention is directed to an arbitrator arrangement that permits both a keyboard and a remote control unit to supply signals, via the single keyboard input of the computer, without confusion. The invention utilizes an electrically programmable array logic device (EPAL) that in operation recognizes signal transmissions from any of the three sources (keyboard, remote control and computer) and in the event of a conflict therebetween, couples the signals based upon an assigned priority. This assures that no erroneous data is received by any of the devices and, as will be seen, is accomplished without the need for additional software.